For several years, the increasing volume of waste and, in particular, domestic refuse, has made it necessary to seek solutions which enable this waste to be treated and exploited.
Consideration has already been given to using such waste as a fuel, but the presence therein of a high water content and of incombustible products only permits energy production at a level which is too low.
In fact, such waste consists of a liquid phase containing only organic products and a solid phase containing metal, inorganic and synthetic materials.
One solution consists in pressing this waste, which makes it possible to obtain residues which are sufficiently dry to form a fuel with an acceptable calorific value, and fluid substances which can be used, according to their nature, in agriculture as soil improvers or as raw materials from which chemical products may be extracted.
Devices are already known which permit this waste to be compressed, and these usually consist of hydraulic presses comprising a feed zone receiving the waste to be treated, and a pressing chamber connected to means for recovery of the liquid phase.
The pressing chamber comprises an entry orifice, an exit orifice and has a cross-section equal to that of a compression piston of a first ram.
The wall of the pressing chamber comprises a multitude of perforations emerging in a channel for discharge of the liquid phase extracted by -w compression of the waste.
The exit orifice of the pressing chamber is generally closed of f by a plug carried by a rod of a second ram opposite the first.
The pistons of the two rams are movable alternately between a first position of compression of the waste and of discharge of the liquid phase, during which the piston of the first ram penetrates into the pressing chamber and the piston of the second ram closes off the exit orifice of the chamber, and a second position of discharge of the solid phase, during which the piston of the first ram continues its travel and the piston of the second ram frees the exit orifice of the pressing chamber.
However, this type of press involves drawbacks.
In fact, taking into account the considerable stresses created at the time of pressing the waste, complete leaktightness is not achieved at the level of the exit orifice of the pressing chamber by the piston of the second ram, so that leakages of liquid may occur and penetrate into the chamber for discharge of the solid phase, thereby reducing the calorific value of the solid phase.
Moreover, the travel of the piston of the second ram is relatively great. This travel corresponds to a thickness of the solid phase, which involves a relatively long response time.